is_tax() not working for event-categories taxonomy

I think I have encountered a bug.
In Events -> Settings -> Pages -> Override with Formats is set to “Yes”. This work great. But, when I want to use the is_tax() function on the taxonomy archive pages, that core function returns false, while it should return true.

When I set the Override with Formats option to “No”, the is_tax() function return true, which is the expected behaviour. Since I like the default styling, I would like to leave the option to “Yes”.

Is this a bug, or is there a workaround by using a custom is_tax() function?